Wheat School: Teaching green-on-green spot spraying systems to identify weeds found in Canada

Work continues on training computer algorithms to unlock the potential of green-on-green spot spraying systems to identify and target the weeds found on Canadian farm fields.

The goal of green-on-green spraying systems is to detect and apply herbicide to weeds that are growing within a green crop. Where green-on-brown spot spraying systems used for burnoff rely on colour differences, a green-on-green system identifies weeds by their leaf shape and other visual features, constantly referencing a growing library of existing images.

There are multiple companies working on green-on-green technology for North America, including France-based Bilberry, which started testing and data collection in Canada during the 2022 growing season.

To begin, in Canada, the company is working on targeting broadleaf weeds in cereal crops (wheat, oats, barley and rye), grassy weeds in canola, and both broadleafs and grasses in corn, explains Adrien Persuy, Bilberry field engineer, in this Wheat School episode.

“As a human, if you can spot the weed in a few meters, then our cameras will be able to detect it. We are looking in front of the boom, we are detecting the weed, and we send the detection order or opening orders to the nozzle controller,” he explains. “Then depending on the speed of the sprayer and so on, it computes the right time to open the correct nozzle.”

The goal is to detect a five centimetre weed at a distance of three to five metres in front of the boom, he says, noting in some cases, the cameras may see a weed, but it will be too small for the algorithm to confidently commit to calling it a weed.

All the companies that are developing green-on-green technology, including Bilberry, are working on refining the artificial intelligence that processes the data coming from their cameras.

“We’ve been working here since April, so we got a lot of pictures of Canadian fields and Canadian weeds. Now we need an AI team to annotate all the pictures, check that we still detect all the weeds, and so on, and then just improve the existing algorithm,” says Persuy.

Everything from weed staging to height of the crop to which way the sun is facing must be accounted for in this algorithm that decides when to tell the sprayer to open individual nozzles. “In Australia, it’s been like three to four years that we are working on a production level and we are still improving it because there are new situations.”

The company has seen an average 80 per cent reduction in the amount of herbicide applied compared with a broadcast application on Australian farms, says Persuy. They’re expecting a lower, but still significant reduction in herbicide volume from the technology in Canada, partly due to Australia having generally drier conditions that are less conducive to weed growth and the shorter spraying season in Canada.

In addition to reducing the amount of herbicide used, the technology could enable the targeting of resistant or hard-to-control weeds with higher rates or more expensive chemistries. The opportunities to use the weed-recognizing technology could also go hand-in-hand with new sprayer designs that allow for multiple products to be applied in a single pass, either via broadcast application or spot spraying.

Persuy says they also see potential to use the high-resolution camera system to selectively apply fungicides and fertilizers based on real-time observations as the sprayer cross the field.

“If this is an issue or a problem or something you want to do, and you are able to do it with your eye as a farmer, then we should be able to do it with camera when we have enough data and enough training of the algorithm,” he says.

One of the biggest questions from farmers and sprayer operators about spot spraying technology remains: if you don’t know what percent of a field will get sprayed, how do you know how much product to mix in the tank? “We cannot answer that question yet. It’s mainly experience,” says Persuy.

As for spraying speed — another common question, he says Bilberry recommends driving 20 km/h (or 12mph.)

Check out the Wheat School episode above for more with Adrien Persuy of Bilberry on the development of green-on-green spraying technology suited for Canadian farming, filmed at Antara Agronomy’s field day held near St. Jean, Manitoba last week.


Pulse School: New green-on-green technology singles out and sprays weeds in-crop

Take a closer look at John Deere’s green-on-green spray technology

The Agronomists, Ep 46: Jason Deveau and Tom Wolf on new spray technology

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